The present invention relates in general to railway car suspensions. More particularly, the present invention relates to retractable auxiliary bumpers for railway car suspensions.
It is known that passenger railway cars use a pneumatic or hydraulic spring suspension to absorb the track shocks and vibrations of the railway trucks so as to provide a safe and comfortable transit for the train passengers. It is also known that the pneumatic or hydraulic spring suspension uses a leveling device to regulate the height of the railway car. U.S. Pat. No. 5,947,031, issued to Polley, describes the use of leveling valves to regulate the height of the railway car and is incorporated herein by reference. These suspensions and leveling devices maintain an essentially constant railway car floor height relative to the railroad track and relative to the height of a station platform. These devices attempt to maintain this constant floor height over an entire load range, that is, from an empty railway car to a full car. A constant railway floor height facilitates safer loading and unloading of passengers, especially disabled persons.
On some existing transit systems, however, the station platforms are positioned below the railway car floor level so that passengers have to step up to board the train or step down to disembark. This uneven height between the railway car floor and the station platform has caused difficulties to passengers, especially ones who are disabled. In an effort to overcome this problem, passenger railway cars have been lowered to align the car floor with the station platform height. With many existing passenger trains, however, it is impractical to lower the railway car floor to the station platform height and still maintain an acceptable dynamic ride quality. The other option of raising the station platforms can be cost prohibitive, especially on older transit systems.
Another effort has been the incorporation into the railway car of a xe2x80x9ckneelingxe2x80x9d operation. With the use of a kneeling operation, the railway car operates dynamically along the railroad track at the upper spring suspension height to provide adequate ride quality and xe2x80x9ckneelsxe2x80x9d to the platform height upon stopping in the station and prior to opening the car doors. The procedure for xe2x80x9ckneelingxe2x80x9d can be briefly summarized as follows. Upon arriving to a complete stop at the station, a sensor on the railway car gauges the station platform height and adjusts the pneumatic or hydraulic spring height by expelling fluid to conform the railway car floor height to the height of the station platform. Prior to leaving the station, and after the doors close, the xe2x80x9ckneelingxe2x80x9d procedure is reversed and the railway car is again raised to operating height.
Problems with xe2x80x9ckneelingxe2x80x9d the railway car occur when the kneeling operation is restricted by the auxiliary suspension mounted to each passenger train. It is commonplace for pneumatic or hydraulic spring suspension systems to include an auxiliary suspension, such as a resilient bumper, to provide safe operation of the passenger train should the pneumatic or hydraulic spring suspension system lose pressure. This auxiliary suspension is located below the car body kneeling position and requires additional deflection beyond the kneeling deflection. Problems arise when the reserve between maximum kneeling deflection and the deflection limit for safe operation is small. With inoperative fluid pressure this can result in excessive suspension deflection so that dynamic clearance limits for safe operation are violated.
The present invention solves the problems known and experienced in the art with respect to passenger cars that xe2x80x9ckneelxe2x80x9d by providing an auxiliary suspension, such as a bumper device, which is depressed below the lowest xe2x80x9ckneelingxe2x80x9d position. In this position, no bumper contact occurs while there is sufficient hydraulic or pneumatic spring pressure to support the car at either operating or xe2x80x9ckneelingxe2x80x9d position. Upon the loss of hydraulic or pneumatic pressure, the auxiliary bumper rises to meet the car body structure and support the car at a level for safe operation. When the pressure is restored to the hydraulic or pneumatic suspensions, the auxiliary bumper retracts to its original position. Significantly, the auxiliary bumper of the present invention does not interfere with normal railcar operation or xe2x80x9ckneelingxe2x80x9d at a station as long as hydraulic or pneumatic pressure is available to the suspension. In addition, the auxiliary bumper supports the railway car at or above the kneeling height thus providing safe operation when suspension pressure is absent.
In an exemplary embodiment, the present invention includes an auxiliary suspension assembly for a railway truck that is operatively connected to the pressurized spring suspension mounted to the railway truck. The auxiliary suspension includes a bumper assembly that further includes a pressurized cylinder, a spool mounted within the cylinder, a spool spring mounted below the spool and within the cylinder, and a resilient bumper pad mounted above the spool. The spool is slidably mounted within the cylinder. A first fluid supply line connects to the spring suspension and a second fluid supply line is mounted in fluid communication with the first supply line. The second supply line also connects to the pressurized cylinder. When there is a change in fluid pressure to the spring suspension in the first supply line there is a change in pressure in the second supply line and cylinder. This change in pressure causes or permits slidable movement of the spool and accompanying bumper pad within the cylinder. This slidable movement effects extension or retraction of the bumper pad relative to the car body.